Due to recent accumulation of physiological knowledge about brain, development in encephalometers, decrease in the cost of high-performance computers, and progression in the field of machine learning and the like, research on Brain Machine Interface (BMI) has been attracting a larger attention (Non-Patent Document 1). “BMI” is an interface connecting brain and machine. BMI measures brain activity signals generated when a person is thinking, or taking a certain action, and picks up an intention of a user by performing signal processing on the measured data.    [Non-Patent Document 1] Toward Brain-Computer Interfacing (Neural Information Processing), MIT Press, ISBN 978-0262042444